The present invention generally relates to gate assemblies which are adapted for use in combination with railroad hopper cars and through which lading, such as finely comminuted or granulated food grade commodities are discharged and, more specifically, to a gate assembly having interchangeable modular components allowing the gate assembly to be easily and readily conditioned for either pneumatic discharge or sanitized gravitational discharge of lading from the hopper car and through the gate assembly.
Rail road hopper cars typically include an underframe for supporting a walled enclosure in which lading is held and transported. As is conventional, the underframe of the car is supported toward opposite ends by well known wheeled trucks which ride on tracks or rails. The bottom of the walled enclosure is usually provided with two or more individual discharge openings for allowing the lading to be discharged from the walled enclosure. The walled enclosure furthermore typically includes sloped or slanted walls or sheets extending upwardly from a periphery of each opening to promote gravitation al movement of the lading toward the opening.
Various methods and devices are known in the art for individually closing the discharge openings in the walled enclosure. Basically, such closure devices or gate assemblies are divisible into two categories. Some hopper cars utilize a sliding door or valve type system for selectively opening and closing the openings at the bottom of the walled enclosure. Alternatively, some hopper cars are provided with pneumatically enabled discharge systems which rely on a pressure differential system for exhausting particulate matter or lading from the enclosure of the hopper car.
A conventional slide gate system includes a frame which is bolted or otherwise secured to the hopper car. The frame likewise defines a discharge opening arranged in registry with the opening at the bottom of the slanting walls on the hopper car. A gate or door is arranged on the frame for sliding movement along a generally horizontal path of travel between open and closed positions relative to the discharge opening on the frame of the gate assembly. A door operating mechanism including one or more racks, typically secured or attached to the door, and rotatably driven pinions is typically used to slide the door between open and closed positions. In an open position, the door of the gate assembly permits the contents of the hopper car enclosure to pass gravitationally from the walled enclosure and through the discharge opening defined by the gate assembly. In a closed position, the door extends across the discharge opening on the frame to shut off the material or matter flow through the gate assembly.
A conventional pneumatic discharge system for hopper cars involves connecting a discharge assembly including a pan-like housing beneath each opening in the bottom of the hopper car. A pneumatic discharge conduit extends from at least one of the sides the pan-like housing in a direction generally normal to a longitudinal axis of the car. One end of the pneumatic conduit opens to the interior of the pan-like housing while an opposite end is adapted for connection to a suction hose or the like for conducting the lading held and stored within the walled enclosure to any suitable discharge station.
The transportation and unloading of finely divided materials, and particularly food stuffs, such as sugar, flour and the like within and from the walled enclosure of the hopper car exacerbates the problems involved with the design and engineering of a railroad hopper car discharge gate assembly. When the lading to be transported involves food stuffs, the FDA has promulgated certain rules and regulations which must be met in order for the hopper car to qualify for transporting food stuffs. Of course, one of the paramount concerns involves designing the hopper car discharge gate assembly such that no foreign matter, accumulation of moisture, or insect infiltration is permitted to contact and possibly contaminate the food stuffs even while they are being discharged or unloaded from the railway hopper car.
Sliding gate closure systems have proven adequate over the years. There are, however, problems inherent with these designs. It is common practice to load a hopper car through roof hatches. The lading, when initially introduced into the walled enclosure, is mixed with air and is very fluid. After standing and as the car travels, however, the lading loses the air film from the finely divided particles and the lading settles and becomes very compact.
As mentioned, the discharge gate assembly is mounted at the bottom of the walled enclosure and, in sliding gate systems, the door must be slidably moved against the friction imposed thereon by the load. Known slide gate systems for hopper cars have relatively large doors to effect discharge of the lading in a timely and efficient manner. Once the door has begun movement, it can be moved through its path of travel with a reasonable amount of torque or input to the door operating mechanism. At the onset of door travel toward an open position, however, such sliding gate systems require a relatively high initial opening force to be imparted to the door.
In those hopper cars which transport food stuffs and utilize a sliding gate for controlling the discharge of lading from the walled enclosure of the hopper car, the frame of the gate assembly is usually equipped with a flanged skirt depending from and arranged in surrounding relation relative to the discharge opening defined by the frame of the gate assembly. The flanged skirt defines a discharge plenum. Typically, an air sled or other form of unloading apparatus is clamped to the flanges on the skirt during a discharge operation thereby permitting the food stuffs in the enclosure of the hopper car to be discharged directly and protectively into the sled and, thus, conveyed away from the hopper car. To inhibit debris, insects, moisture, clay and other forms of debris from contaminating the underside of the door and interior of the discharge plenum during transport of the hopper car, such sliding gate systems typically include a sanitary plate or cover plate which slides between open and closed positions in a horizontal plane generally parallel to the door to close the discharge plenum and protect the underside of the door during transport of the hopper car. Of course, known sanitary plates or cover plates are neither designed nor configured to withstand the load which can be placed thereon by the commodity in the enclosure of the hopper car.
Another problem has been identified with sliding gate systems when the lading in the walled enclosure involves fine granular food stuffs. As will be appreciated, to enable the sliding door to operate between positions, an operating gap or opening must be provided between the frame of the gate assembly and the door. Such gap or opening is typically provided between the skirt on the frame and the door. It is through this opening that contaminants, moisture, and related debris can enter the discharge plenum, thus, contaminating the food stuffs upon discharge of the lading from the hopper car and through the discharge plenum.
Arranging seals or gaskets about the discharge opening of the gate assembly frame in an attempt to close or seal such openings has often resulted in the seal or gasket being pulled from the gate assembly. The racks on the door coupled with the sliding movement of the door between open and closed positions further complicate the ability to seal the door against contaminants passing into the discharge plenum or opening on the frame of the gate assembly. Moreover, the required need to seal an element of the gate assembly movable in opposite linear directions furthermore complicates the sealing ability of the gate assembly.
It is known in the art to mount a pan-like structure or housing including the pneumatic discharge conduit to the frame of the gate assembly beneath the sliding door. The pan-like structure or housing is typically fastened to the walled enclosure of the hopper car beneath the sliding door with a plurality of fasteners. As such, the hopper car can function in either a gravitational discharge mode or a pneumatic discharge mode. Of course, valuable time is consumed and lost by affixing and removing the pan-like housing from the hopper car depending upon which type of discharge operation is required or desired. Mounting and arranging the pan-like structure or element above the sliding door of the gate assembly has been found to obstruct the flow of material from the walled enclosure in a gravitational mode of material discharge. Moreover, it is desirable to provide only a single drive mechanism for operating the components of the gate assembly thereby simplifying its operation.
Thus, there remains a need and a desire for a gate assembly for a railroad hopper car which can be conditioned for either pneumatic or gravitational discharge of lading from the walled enclosure of the hopper car and which utilizes but a single operating mechanism for operating the components of the gate assembly in timed relation relative to each other. Moreover, it is desirable to provide a gate assembly for a railroad car having a sliding door and wherein the operating mechanism imparts a high impactual opening force against the door during initial stages of its movement toward an open position. Additionally, there is a need and desire for a gate assembly for a railroad hopper car including modular components permitting the gate assembly to be easily and readily conditioned for pneumatic and/or gravitational discharge or gravitational discharge only simply by interchanging the components thereof.
In view of the above, one of the salient features of the present invention involves the provision of a railroad car discharge gate assembly which can be easily and readily conditioned for either pneumatic and/or gravitational discharge or gravitational discharge only of materials therethrough. As is conventional, the gate assembly of the present invention includes a rigid frame preferably having a rectangular configuration and defining a generally centralized discharge opening. Moreover, the gate assembly of the present invention is provided with a door or first element slidable on the frame along a predetermined path of travel extending across the discharge opening. Unlike other known railroad car discharge gates, however, the present invention allows for either of two interchangeable modular components or elements to be easily and readily mounted on the frame for sliding movement along a predetermined path of travel beneath the door and across the discharge opening. One modular element is configured as an open top pan assembly including a pneumatic port allowing for pneumatic discharge of materials. The other modular component of the present invention is preferably configured as a flat plate for inhibiting debris from contaminating an underside of the gate and unloading attachment areas. Accordingly, a primary object of this invention is to provide a gate assembly specifically designed to allow for either pneumatic and/or gravitational discharge or gravitational discharge only of materials therethrough.
A unique drive mechanism forms part of the gate assembly of the present invention. According to the present invention, the drive mechanism is selectively engagable with and capable of selectively moving either the door or the modular element arranged on the gate assembly in combination with the door toward an open position and relative to the frame of the gate assembly. As is conventional, the drive mechanism includes an operating shaft assembly supported on the frame for rotation about a fixed axis.
The drive mechanism of the present invention further includes a rack and pinion assembly arranged in combination with the operating shaft assembly. The rack and pinion assembly includes a pair of laterally spaced pinions arranged on and rotatable with the operating shaft assembly. The rack and pinion assembly further includes a pair of laterally spaced racks or toothed tracks arranged in intermeshing relation relative to the pinions. Each of the racks, are carried on the frame of the gate assembly preferably on opposed sides of the door and in slidable relation relative to the door and either of the interchangeable modular components. In a preferred form, the racks are spaced from the frame so as to reduce the coefficient of friction therebetween. In a most preferred form, ultra-high molecular weight polyethylene is disposed between the frame of the gate assembly and each of the racks to promote sliding movements of the racks relative to the frame of the gate assembly.
In a preferred form, the drive mechanism further includes an apparatus arranged inoperative combination with the rack and pinion assembly for selectively coupling either the door or the modular component or both to the drive mechanism. The apparatus includes a control rod preferably mounted for endwise movement and having an actuator arranged thereon for operably engaging either the door or the modular component arranged on the gate assembly. In a preferred form, the actuator is positioned in the path of movement of either the door or the modular component arranged in combination with the door such that when the drive mechanism is operated, either the door or modular component will be moved toward an open position in response to rotation of the operating shaft. Alternatively, in a most preferred form, the rack and pinion assembly is locked thereby inhibiting rotation of the operating shaft assembly, thus, preventing movement of either the door or the modular element arranged in combination with the door on the gate assembly.
Moreover, the apparatus of the drive mechanism is preferably provided with a detent mechanism for releasably holding the actuator in a selected position to operably engage either the door or the modular component arranged in combination on the gate assembly. The apparatus of the drive mechanism furthermore preferably includes a spring for resiliently urging the control rod and the actuator carried thereby toward a predetermined position. In a preferred form, cam structure is arranged in combination with the apparatus for automatically positioning the control rod and thereby the actuator relative to the frame of the gate assembly when the apparatus is positioned adjacent an end wall of the frame of the gate assembly.
Another salient feature of the present invention involves providing a lost motion connection the drive mechanism and the door of the gate assembly. Rotation of the operating shaft assembly initially results in sliding movement of only the racks without corresponding linear movement of the door. Notably, only the racks slidably move relative to the frame and the door during the collapse of the lost motion connection. Because only the racks move, the operating shaft assembly will have a predetermined range of free rotation. Upon collapse of the lost motion connection, a relatively high impactual opening force will be applied to the door thereby enhancing opening of the door. Upon collapse of the lost motion continued rotation of the operating shaft assembly will effect substantially simultaneous linear movement of the rack and door relative to the frame. Moreover, and besides offering a relatively high impactual opening force to the door, the lost motion connection between the door and the operating shaft maintains the door and the other modular element arranged in combination with the door in timed relation relative to each other.
In a preferred form, a tamper seal can be provided in combination with the operating shaft assembly. The purpose of the tamper seal is to provide a visual indication of whether the operating shaft assembly has been operated to move either the door or that modular component arranged on the gate assembly in combination with the door toward an open position.
The seal structure is preferably comprised of an elongated and hollow elastomeric member configured for energization regardless of the direction of movement of either the door or the modular component associated with the door. The elastomeric member of the seal structure has a first radial surface arranged in tangential engaging relation relative to a flat surface on the door or the modular component associated with the door thereby allowing the door or the modular component to move in either linear direction while maintaining a sealing engagement therewith. The radial surface preferably has an elongated rib projecting therefrom and extending therealong to enhance the sealing ability of the seal structure relative to either the door or the modular component associated with the door.
In a most preferred form, the elastomeric member of the seal structure has a centralized mounting portion with an aperture or opening defining an axis extending generally parallel to the path of travel of the door. The first radial surface on the elastomeric member is disposed to one side of the axis. In an alternative form, the elastomeric member has a second radial surface disposed on an opposite side of the seal structure. The second radial surface is disposed generally tangential to a flat surface on the door or the modular component associated with the door thereby allowing the door or the modular component to move in either linear direction while maintaining a sealing engagement therewith. As will be appreciated, two sealing surfaces allows the seal to be compressed between the door and the modular component thereby acting as a compression/wiper seal or allowing for reversal of the seal structure thereby prolonging the useful life thereof.
In a preferred form, the frame of the gate assembly furthermore includes wall structure or skirt arranged in surrounding relation relative to and depending from the discharge opening of the frame to define a discharge plenum through which material passes. To facilitate connection of a discharge apparatus thereto, the lower end of the depending walled structure or skirt is configured with flanges which operate in a conventional manner with an inlet to the unloading apparatus thereby enhancing transference of particulate materials through the gate assembly and into the discharge apparatus. As will be appreciated, when the modular component arranged in combination with the door on the gate assembly is configured as a flat or sanitary plate, such plate inhibits debris from contaminating the underside of the door and the plenum chamber.
When the gate assembly of the present invention is mounted to a hopper car, it allows the gate assembly to be readily and easily conditioned for either gravitational or pneumatic discharge of food grade materials from an enclosure on the car wherein the food grade materials are held and transported. Either of two modular components are fitted to the gate assembly and move along rails projecting outwardly from the frame. During operation, the apparatus of the drive mechanism is suitably conditioned to properly position the actuator of the apparatus in the path of travel of movable elements on the gate assembly thereby effecting their movement when the operating shaft assembly is rotated. The lost motion connection of the drive mechanism allows a relatively high impactual force to be imparted to the door during the initial opening thereof. Moreover, the seal structure preferably forming a part of the present invention inhibits debris from passing between the elements and the frame thereby protecting the food grade commodity from contamination.
These and other objects, aims and advantages of the present invention will be readily and quickly appreciated from the following detailed description, appended claims, and drawings.